Piezoelectric transducer mounting apparatus

ABSTRACT

A method of and apparatus for mounting a ceramic transducer to substantially reduce stresses produced therein as a result of its operation or external forces. The improvement comprises cylindrical rings which, while having high axial stiffness, have relatively low radial stiffness and therefore allow the transducer to flex or expand radially with respect to the mounting means while being axially held in place.

3,030,606 4/1962 Harris 310/9.1 3,054,084 9/1962 Parssinen et a1 310/9.1 2,906,991 9/1959 Camp 3 10/9.l 3,277,436 10/1966 Fitzgerald et a1. 340/10 3 ,441,754 4/1969 Heny 310/87 Primary Examiner-Milton O. Hirshfield Assistant Examiner-B. A. Reynolds Att0rneys-Charles J. Ungemach, Ronald T. Reiling and Charles L. Rubow ABSTRACT: A method of and apparatus for mounting a ceramic transducer to substantially reduce stresses produced therein as a result of its operation or external forces. The improvement comprises cylindrical rings which, while having high axial stiffness, have relatively low radial stiffness and therefore allow the transducer to flex or expand radially with respect to the mounting means while being axially held in place.

PATENTEDHAY 4mm INVENTOR. IRVIN E GERKS BY fi p a ATTORNEY PIEZOELECTRIC TRANSDUCER MOUNTING APPARATUS The present invention pertainsgenerally to transducers and more specifically to piezoelectric transducers.

In the prior art many methods have been utilized to protect transducer mechanisms against shock. However, in all known instances where the mounting means allows movement of the transducer, mounting means has been in the form of a spring to allow movement in the axial direction. While the present invention allows movement in the axial direction, such movement-is only incidental and primarily due to the resilience of .the mounting means in the radial direction. Without radial cylinder is shown with an enlarged portion 12 and a reduced portion or neck 14. Through the center of support 10 is a bolt 16 which connects support 10 to a further support 18. Support 18 has a circular seat 20 into which is seated one end of a cylindrical ring, radially compliant means or resilient means 22. Support 10 has a cylindrical seat 24 into which is seated one end of a cylindrical ring, radially compliant means orr'esilient means 26. An exaggerated space designated as 28 is shown between supports 10 and 18 which in actuality is very small and is utilized to axial allow movement of the entire support 10 with respect to the support 18 under high shock conditions and further to allow freedom of movement of a piezoelectric transducer element 30 which is shown situated between rings 22 and.26. However, excessive axial movement of support 10 with respect to support 18 is prevented by contact between the supports under high shock conditions. It will be noted that transducer means 30 has circular seats 32 and 34 which contact the other ends of rings 22 and 26 respectively.

As previously indicated, the rings 22 and 26 have a high axial stiffness while having a relatively low radial compliance or stiffness. As will be realized, when a cylindrical transducer such astransducer 30 is energized by electrical signals, it expends radially. If this transducer is rigidly mounted, stresses are produced therein, mainly at its edges, due to the fact that the center of the transducer expands while the ends are constrained. This tends to destroy the transducer at an early stage in operational life.

The present invention on the other hand utilizes rings 22 and 26, having high axial stiffness and resistance to deformation, which are seated in the seats 20, 32, 34 and 24 to prevent radial movement of seated ends 20, 24. with respect to the transducer axis while permitting radial movement or expansion of ends 32, 34. When a signal is applied to the transducer 30 to cause it to expand in a radial direction, the compliant rings 22 and 26 pivot on seats 20 and 24 to allow movement of the transducer without building radial stresses therein.

Under high shock conditions in one direction along the transducer axis bolt 16 will prevent excessive movement of support 10 in an outward direction with respect to support 18 since the bolt is under tension in the original mounting of the transducer. Moreover, the depth of the seats will prevent 5 realignment of the rings with respect to theseats. Upon shock in the other direction along the transducer axis, excessive movement in the inward direction will be prevented because of the limited space 28. Some rings 22 and 26 by flexing in the radial direction to allow movement is permitted by closure of the gap 28. It has been found that the present mounting allows a transducer to within shocks of as much as 60 percent greater than permitted by the best previous designs, and thus greatly increases the life of the transducer under shock conditions.

ln summary, the invention lies in the use of radially resilient or compliant rings which allow movement of a transducer relative to rts support in the radial direction while preventing substantial axial movement. If the rings are not used, the transducer may, after an excessive shock, return to its initial position with such force as to destroy the transducer. As will be noted, the present embodiment prevents substantial axial movement because the various parts are held in compression by the bolt 16.

I wish to be limited only by the scope of the claims in this application for United States Letters Patent.

lclaim:

l. Piezoelectric transducer apparatus for use in environments of high shock along an axis comprising:

a tubular piezoelectric transducer element aligned with the axis, said transducer element having a predetermined mean diameter and first and second ends;

first and second tubular supporting elements each having first and second ends and having mean diameters substantially equal to the mean diameter of said transducer element, said first and second supporting elements being aligned with the axis and positioned so that the first ends thereof contact the first and second ends respectively of said transducer element;

a first mounting member having surface thereon adapted to hold the second end of said first supporting element;

a second mounting member having a surface thereon adapted to hold the second end of said second supporting element; and

means for drawing said second mounting member toward said first mounting member along the axis so as to maintain said transducer element and said supporting elements in compression.

2. The apparatus of claim 1 wherein said first and second tubular supporting elements have walls of a thickness substantially less than the dimensions of said supporting elements parallel to the axis.

3. The apparatus of claim 1 wherein said first mounting member includes a portion extending along the axis through said transducer element and said first and second supporting elements to a position proximate. said second mounting member, so that under high compressive shock conditions said first and said second mounting members come into contact, thus preventing further compression of said transducer element and said supporting elements along the axis. 

2. The apparatus of claim 1 wherein said first and second tubular supporting elements have walls of a thickness substantially less than the dimensions of said supporting elements parallel to the axis.
 3. The apparatus of claim 1 wherein said first mounting member includes a portion extending along the axis through said transducer element and said first and second supporting elements to a position proximate said second mounting member, so that under high compressive shock conditions said first and said second mounting members come into contact, thus preventing further compression of said transducer element and said supporting elements along the axis. 